Furnace won't kick on
Does the furnace light off at all? Or is it just a case of the thermostat not reaching the temperature you have it set for?...I assume the latter or else you whave not had heat at all in awhile. If it is the thermostat, is it a digital or statndard mercury bulb style?....You can calibrate the temperature sensor on a mercury bulb by adjusting the small screw on the back of the cover.....these are not real reliable, but you should be able to get it close enough.
If it isnt the themostat, then check and see if the furnace has any error codes on the board ( assuming you have a board in your furnace).